1. Field of the Invention
The invention relates to a DC-DC converter; in particular, to a DC-DC converter, a timing signal generating circuit, and operating methods thereof.
2. Description of the Prior Art
Please refer to FIG. 1. FIG. 1 illustrates a functional block diagram of a one-shot timing generator of a conventional DC-DC converter. As shown in FIG. 1, the one-shot timing generator TG is used to output a pulse signal ONT_OUT to control a gate control unit and further control a gate driver to output a switch conducting signal to an output stage. However, in practical applications, the pulse width of the pulse signal ONT_OUT is not always equal to the pulse width of the switch conducting signal due to non-ideal factors such as signal propagation delay, driver delay, or other delay caused by parasitic capacitances. The on-time (Ton) will be affected by these non-ideal factors to generate an error time, and the proportion of the error time under different input voltages will be different; therefore, it will cause an error generated in the system operation frequency.
Please refer to FIG. 2. FIG. 2 illustrates a curve diagram of the on-time (Ton) varied with the reciprocal of the input voltage (VIN). As shown in FIG. 2, the intercept 52.041 of the curve y=3532.8×+52.041 with the vertical axis y is the error time of the on-time (Ton) under the non-ideal condition. As shown in FIG. 3, the system operation frequency (f) will be affected by this error time, and the system operation frequency (f) under different input voltages (VN) will be also different. Especially, when the input voltage is at high-level, the system operation frequency will become lower, and the normal system operation will be affected.
Therefore, the invention provides a DC-DC converter, a timing signal generating circuit, and operating methods thereof to solve the above-mentioned problems occurred in the prior arts.